According to a study published in Nanoscale Horizons, researchers from Kaunas University of Technology (KTU) in Lithuania and scientists from Japan collaborated to create a novel nanolaser.
Assembled nanocube nanolaser. Image Credit: Kaunas University of Technology
Although the size of this laser is so small that its structure can only be seen with a strong microscope, its potential is enormous. This invention has potential applications in early medical diagnostics, data communication, and security technologies and is a fundamental tool for studying light-matter interactions.
Depending on the application, lasers differ in how light is amplified and created, determining the radiation's color and the laser beam's quality.
Nanolasers are lasers that use structures a million times smaller than a millimeter to generate and amplify light, and the laser radiation is generated in an extremely tiny volume of material.
Dr Mindaugas Juodėnas, Study Author and Senior Researcher, Kaunas University of Technology
The Laser’s Operating Principle Resembles a Hall of Mirrors
Such nanolasers have been studied and produced for quite some time. However, the version developed by KTU scientists is unique in terms of manufacturing technique. It employs silver nanocubes neatly placed on a surface and filled with an optically active material. This establishes the method required to magnify light and generate the laser effect.
Juodėnas added, “The silver nanocubes are extremely small, monocrystalline silver particles with excellent optical properties. It is an essential part of the nanolaser we have developed.”
The nanocubes are synthesized using a novel technology developed by KTU partners in Japan, ensuring their perfect shape and quality. These nanocubes are then organized into a two-dimensional structure utilizing nanoparticle self-assembly.
During this technique, particles naturally arrange themselves from a liquid medium into a pre-patterned template.
When the template parameters coincide with the optical characteristics of the nanocubes, a special phenomenon known as surface lattice resonance is produced, enabling effective light production in an optically active medium.
While conventional lasers use mirrors to achieve this effect, the nanolaser developed by KTU researchers employs a surface coated with nanoparticles.
“When the silver nanocubes are arranged in a periodic pattern, light gets trapped between them. In a way, the process reminds a hall of mirrors in an amusement park, but in our case, the mirrors are the nanocubes and the visitor of the park is light,” explained Juodėnas.
International Funding Helped Develop the Idea
By utilizing high-quality, easily made nanomaterials such as silver nanocubes, the laser requires a record-low amount of energy to operate, allowing lasers to be mass-produced.
“Chemically synthesized silver nanocubes can be produced in hundreds of milliliters, while their high quality allows us to use nanoparticle self-assembly technology. Even if their arrangement is not perfect, their properties make up for it,” added Juodėnas.
However, the initial simplicity of the procedure, which should have piqued attention, turned Lithuanian research funding organizations off.
Sceptics questioned whether the simple method we were using would be able to create structures of high enough quality for a working nanolaser.
Sigitas Tamulevičius, Professor, Kaunas University of Technology
The KTU Materials Science Institute team got funding from an international organization based on their strong belief in the quality of their nanolaser. According to Juodėnas, the idea was considered promising.
He stated, “After a lot of work and a number of experiments, we have proved that even imperfect arrays can be effective if high-quality nanoparticles are used.”
A neat arrangement of nanoparticles, which is also employed in another invention by KTU researchers to create anti-counterfeiting marks, has already obtained international recognition and approval from the US and Japanese patent offices.
The nanolaser developed by KTU researchers could be employed as a light source in ultra-sensitive biological sensors for diagnosing diseases or real-time monitoring. It could also be used in small photonic chips, identifying technologies, and authentication systems, where the beam’s distinct structure is critical. Furthermore, it might help fund fundamental research into how light interacts with matter at the nanoscale.
Journal Reference:
Juodėnas, M. et. al. (2024) Lasing in an assembled array of silver nanocubes. Nanoscale Horizons. doi.org/10.1039/D4NH00263F